The present invention generally relates to air bags and more particularly to driver type air bags.
Many inflators that are used to inflate a driver side air bag resemble a shortened cylinder (a small height/diameter ratio). The side wall of the cylinder includes a plurality of small exit openings through which inflation gas exits the inflator and enters into an inlet of the air bag. Inflators include a small quantity of propellant or gas generant material. To prevent moisture from entering into the propellant, most inflators wrap the propellant with a metal foil or, alternatively, adhere a metal foil to the inside surface of the inflator""s side wall. This foil obscures and blocks the plurality of exit holes or exit ports, thus providing a hermetic seal.
After the propellant is ignited, inflation gas is produced within the still closed inflator. At some level of pressure, the heated inflation gasses cause the foil to burst through the exit ports, thereby permitting the inflation gas to inflate the air bag. Occasionally, that portion of the foil sealing the exit port will become airborne and be pushed into the air bag by the out rush of inflation gas. This small piece of foil, which may now be heated by the inflation gas, could possibly flow past the various heat shields typically used in a driver side air bag and might impinge on the face panel or rear panel of the driver side air bag.
In addition to the small piece of foil, certain other particulates associated with the generant or propellant may flow out of the inflator into the air bag. To lessen the amount of deployment-generated particulates, many inflators employ metal or ceramic filters. These filters are placed about and downstream of the propellant and upstream of the metal foil barrier that blocks the exit openings. In a broad sense the small piece of metal foil may be considered as another particulate, however, this type of particulate cannot be filtered by the particulate filter, which is upstream of the foil.
In the present invention, the entrapment of these foil particles is accomplished primarily by the physical interaction and characteristics of an inner flexible bag and secondarily due to the physical characteristics of a retaining ring.
It is an object of the present invention to provide an improved air bag module.
Accordingly the invention comprises: an air bag module assembly comprising: an inflator having at least one exit port with a thin layer of burst material blocking at least one exit port, the burst material bursting forth from the exit port during activation of the inflator; an air bag assembly comprising an inflatable first bag and an inflatable second bag, the second bag located within the first bag, the second bag including an opening to receive the inflator wherein prior to activation, opposed portions of the second bag, radially outboard of the inflator, are formed into respective flaps, which are overlaid and positioned on a top of the inflator to provide a tortuous path for of any particles including particles of burst material.